In the field of non-impact printing, the most common types of printers have been the thermal printer and the ink jet printer. When the performance of a non-impact printer is compared with that of an impact printer, one of the problems in the non-impact machine has been the control of the printing operation. As is wellknown, the impact operation depends upon the movement of impact members such as wires or the like and which are typically moved by means of an electromechanical system which is believed to enable a more precise control of the impact members.
The advent of non-impact printing as in the case of thermal printing, brought out the fact that the heating cycle must be controlled in a manner to obtain maximum repeated operations. Likewise, the control of ink jet printing in at least one form thereof must deal with rapid starting and stopping movement of the ink fluid from a supply of the fluid. In each case, the precise control of the thermal elements and of the ink droplets is necessary to provide for both correct and high-speed printing.
In the matter of ink jet printing, it is extremely important that the control of the ink droplets be precise and accurate from the time of formation of the droplets to depositing of such droplets on paper or like record media and to make certain that a clean printed character results from the ink droplets. While the method of printing with ink droplets may be performed either in a continuous manner or in a demand pulse manner, the latter type method and operation is disclosed and is preferred in the present application as applying the features of the present invention. The drive means for the ink droplets is generally in the form of a piezoelectric crystal element to provide the high-speed operation for ejecting the ink through the nozzle while allowing time between droplets for proper operation. The ink nozzle construction must be of a nature to permit fast and clean ejection of ink droplets from the print head.
In the ink jet printer, the print head structure may be a multiple nozzle type with the nozzles aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner. The ink droplet drive elements or transducers may be positioned in a circular configuration with passageways leading to the nozzles. Alternatively, the printer structure may include a plurality of equally spaced horizontally alinged single nozzle print heads which are caused to be moved in back and forth manner to print successive lines of dots making up the lines of characters. In this latter arrangement, the drive elements or transducers are individually supported along a line of printing.
Since it is desirable to eliminate a curving transition section between the drive elements and the nozzles as in the case of the circular arrangement, it is proposed to provide an array of ink jet transducers in parallel manner for use in a compact print head.
Representative prior art in the field of ink jet print heads includes U.S. Pat. No. 3,373,437 issued to R. G. Sweet et al. on Mar. 12, 1968, which discloses a fluid droplet recorder with a plurality of jets and wherein a common fluid system supplies ink to an array of side-by-side nozzles.
U.S. Pat. No. 3,683,212 issued to Steven I. Zoltan on Aug. 8, 1972, discloses an electroacoustic transducer coupled to liquid in a conduit which terminates in a small orifice through which droplets of ink are ejected.
U.S. Pat. No. 4,005,440 issued to J. R. Amberntsson et al. on Jan. 25, 1977, discloses a printing head of smaller size and wherein the openings of the capillary tubes are located closer to one another.
U.S. Pat. No. 4,014,029 issued to R. Lane et al. on Mar. 22, 1977, discloses a nozzle plate having at least two rows of nozzles and effecting a staggered nozzle array wherein the nozzles in one row are laterally displaced with respect to the nozzles in another row to print a portion of a line at a time, a line at a time or several lines at a time.
U.S. Pat. No. 4,128,345 issued to J. F. Brady on Dec. 5, 1978, discloses a fluid impulse matrix printer having a two-dimensional array of tubes in a 5.times.7 matrix to print a complete character at a time.
U.S. Pat. No. 4,158,847 issued to J. Heinzl et al. on June 19, 1979, discloses a piezoelectric operated print head having twin columns of six nozzles.
U.S. Pat. No. 4,189,734 issued to E. L. Kyser et al. on Feb. 19, 1980, discloses a writing fluid source feeding drop projection means which ejects a series of droplets through a column of seven nozzles with sufficient velocity to traverse a substantially straight trajectory to the record medium.